ORLANDO, Fla. -- Shaquille O'Neal, the man with four rings, 28,596 career points and scores of nicknames, has finally decided to call it quits, ending one of the most colorful careers in NBA history that will surely culminate with a Hall of Fame induction.

O'Neal, 39, officially announced his retirement Wednesday using the new social media tool Tout, a real-time video messaging service to announce to fans: "We did it. Nineteen years baby. I want to thank you very much, that's why I'm telling you first, I'm about to retire. Thank you, talk to you soon."

O'Neal said he wasn't prepared yet to reminisce about his long and prolific career, which produced three championships with the Lakers and one with the Heat. "Let's save that for the press conference on Friday," said O'Neal, who will hold that media event at his Isleworth home.

Celtics spokesman Jeff Twiss says that O'Neal has not notified the team of his plans.

O'Neal signed a two-year contract with the Boston Celtics last summer but a persistent Achilles injury will prevent him from fulfilling the terms of the deal. O'Neal first injured his right Achilles on Christmas Day and was able to play only in two of the final 35 games of the regular season.

On April 3 against Detroit, O'Neal returned to the court after a two-month absence and scored six points in a spirited 5 minutes and 29 seconds before coming up lame and limping off the floor. Although his injury was listed as a strained calf, O'Neal said it was the Achilles flaring up again.

"I felt like someone had shot me in the back of my leg," he said.

O'Neal did not play again in the regular season. He sat out the New York Knicks playoff series then tried to return in Game 3 of the Eastern Conference semifinals against his old team, the Miami Heat. O'Neal logged 8½ minutes in the 97-81 victory but woke up in considerable pain the next morning. His final game was two days later, when he toiled for three minutes of Game 4 before Celtics coach Doc Rivers pulled him for good.

In the final weeks of the the playoffs, O'Neal, over the objections of team physician Brian McKeon, had "more than five" cortisone shots in his Achilles in an attempt to play against the Heat.

"Doc (McKeon) kept telling me, 'No, no,' but I wanted to play so badly," O'Neal said. "My feeling was, 'If it ruptures, it ruptures.' The Celtics were so good to me I wanted to do everything I could to get back on the court for them."